Control mechanism for sewing machine thread tension device



Dec. 10, 1963 s. J. KETTERER 3,113,539

CONTROL MECHANISM FOR SEWING MACHINE THREAD TENSION DEVICE Filed Feb. 26, 1962 3 Sheets-Sheet 1 INVENTOR.

ATTORNEY Fig.l

Dec. 10, 1963 5. J. KETTERER 3,113,539

CONTROL MECHANISM FOR SEWING MACHINE THREAD TENSION DEVICE 3 Sheets-Sheet 2 Filed Feb. 26 1962 mmvrox. Stanley J. Kefferer ATTORNEY WITNESS flWWg;

Dec. 10, 1963 S. ,I. KETTERER CONTROL MECHANISM FOR SEWING MACHINE THREAD TENSION DEVICE Filed Feb. 26, 1962 3 Sheets-Sheet 3 INVENTOR. Stanley J. Kefferer ATTORNEY United States Patent 3,113,539 CONTRGEL T-MIECHANISM FOR SEWING MACHINE E 2 =15 AD TENSION DEVICE Stanley J. Ketterer, Morris Plains, N..l., assignor to The Singer Company, a corporation of New Jersey Filed Feb. 26, 1962, Ser. No. 175,692 3 Claims. (Cl. 112255) This invention relates to sewing machines and more particularly to sewing machines with needle thread tensioning devices having tension releasing means associated therewith.

It is an object of this invention to provide a novel tension releasing means for a sewing machine thread tensioning device by which the effectiveness of the thread tensioning device once released may be reestablished in only one predetermined position of the sewing machine stitch forming instrumentalities.

A further object of this invention is to provide a tension releasing means for a sewing machine thread tensioning device which may be rendered elfective by any one of a plurality of separate operating means, a novel latch means for maintaining the tension releasing means eifective until the sewing machine stitch forming instrumentalities reach a predetermined position, and a means rendered effective when said tension releasing means is rendered effective by one of said plurality of separate operating means for circumventing said latch means.

Another object of this invention is to provide in a lock stitch sewing machine having a mechanism for replenishing thread on a bobbin in place in the loop taker during continued motion of the stitch forming instrumentalities as is required for the formation of lock stitches, a tension releasing means for the needle thread tensioning device which may be rendered effective either by the bobbin thread replenishing mechanism or by a presser lifting mechanism, and a means operative only when said tension releasing means is rendered effective by said bobbin thread replenishing mechanism for maintaining the tension releasing means efiective until the sewing machine stitch forming instrumentalities reach a predetermined position.

The control mechanism of this invention for the sewing machine thread tensioning device is particularly well adapted for use in a lock stitch sewing machine of the type including a bobbin thread replenishing mechanism as illustrated and described in my co-pending United States patent application Serial No. 133,896, filed August 25, 1961 to which reference may be had. Generally, in the operation of the bobbin thread replenishing mechanism of my above referenced to co-pending application, thread from the sewing needle is directed to and wound on the bobbin in place in the loop taker during continued motion of the needle and loop taker as is required for the formation of lock stitches. It is known during such bobbin thread replenishing operation to release the needle thread tensioning device so as to reduce the stress which might otherwise be imposed on the needle thread as is being wound on the bobbin. Upon completion of the bobbin thread replenishing operation, all of the parts of the sewing machine have heretofore been immediately returned to a position suitable for sewing operations, and this has heretofore included an immediate return of the needle thread tension device to effectiveness. Inasmuch as completion of bobbin thread replenishing operations ice might occur without correlation with any particular position of the stitch forming instrumentalities of the sewing machine it will be apparent that a serious detriment to satisfactory sewing can occur should the needle thread tension device be reestablished to efiectiveness while the take up mechanism of the sewing machine is taking up a loop of thread. In this event the thread necessary to supply the take up mechanism instead of being drawn from the needle thread supply, will be drawn instead from the bobbin and can turn the bobbin backwardly with such force as to cause a backlash with considerable thread being spilled from the bobbin and subject to snarling, engagement by the loop taker or the like which results in imperfect stitching or thread breakage.

This invention provides a means for maintaining the needle thread tension device released at the completion of bobbin thread replenishing operations until the sewing machine take up has reached a point of maximum expansion of a thread loop thus preventing backlash and spilling of the bobbin.

In conventional operation of a sewing machine, for instance, after replenishment of the bobbin thread has been concluded in the sewing machine of my above referenced to patent application Serial No. 133,896, there are many occasions when release of the needle thread tension is desired and in which it would be detrimental to satisfactory stitch formation for the needle thread tension to remain released until the sewing machine take up member reaches a maximum take up of its thread. For instance, it is a common sewing practice in turning a sharp seam corner to stop the sewing machine with the needle penetrating the work, to raise the presser device and thereby release the needle thread tension device, to turn the work, and then to lower the presser device and continue stitch formation in a new direction on the work. If in this cornering operation, the needle thread tension were to remain released until the take up device has reached its highest point, serious looping and imperfect stitch formation would occur for several succeeding stitches.

This invention provides for a release of the needle thread tension device by the presser lifting mechanism, with an immediate restoration to eifectiveness of the needle thread tension device when the presser mechanism is lowered.

In the accompanying drawings of a preferred embodiment of this invention,

FIG. 1 represents a front elevational view of a sewing machine having this invention applied thereto and with a portion of the sewing machine bracket arm broken away and illustrated in a vertical cross section,

FIG. 2 illustrates an enlarged end elevational view of the bracket arm of the sewing machine illustrated in FIG. 1 with the end cover plate removed illustrated in solid lines the position of the parts maintaining the thread tension device released,

FIG. 3 is a fragmentary end elevational view of the sewing machine bracket arm of FIG. 2 with the parts illustrated with the thread tensioning device effective, and

FIG. 4 represents a cross sectional view taken substantially along line 44 of FIG. 3.

Referring to FIG. 1 of the drawings 11 indicates the bed portion of a sewing machine frame from which rises a standard 12 carrying a bracket arm 13 which overhangs the bed. Journaled in the bracket arm is a main drive shaft 14 to which is geared a shaft 15 in the standard, and a bed shaft 16 providing a gear drive for a loop taker shaft 17 journaled in the bed and carrying a loop taker 18 fast thereon. A crank member 19 fast on the main drive shaft 14 carries a crank pin 2%) which is embraced by a needle thread take up lever 21 and by a needle bar drive link 22. The drive link 22 is pivoted in turn on a needle bar 23 carried for endwise reciprocation on the bracket arm 13 to which is secured a needle 24 which by virtue of the shafts 14, 15 and 16 is driven in timed relation with the loop taker as is required for the formation of lock stitches.

The sewing machine preferably includes a bobbin thread replenishing mechanism which is illustrated and described in detail United States application Serial No. 133,896.

For an understanding of this invention however, a bobbin journaled in the loop taker will be replenished with thread from the needle 24 when a. bobbin winding member 31 carried on a rod 32 slidably axially of the loop taker shaft 17 is elevated into engagement with the bobbin. Bobbin thread replenishment is controlled by an operator influenced dial 33 and carried in the machine standard and having a cam 34 fast thereon. A lever 35 in the standard is influenced by the cam 34 to depress a link 36 thereby turning a bobbin replenishing lever 37 in the bed in a clockwise direction as viewed in FIG. 1 to elevate the bobbin winding member 31 and also turning a lever 38 fulcrumed at 32* in the bracket arm clockwise as viewed in FIG. 1 for the purpose of releasing the needle thread tensioning device.

Referring to FIGS. 2 and 3 the needle thread tensioning device is indicated at as and includes a stud 41 on which are loosely carried a plurality of pressure discs 42 between which the needle thread is directed as it is passed to the needle. A beehive spring 43 constrained on the stud by means of a nut 44 bears against a washer 45 formed with a tank 46 accommodated in a transverse slot 47 in the stud. The beehive spring 43 which ordinarily biases the thread engaging pressure discs 42 of the tension device against a shoulder 48 on the stud, may be collapsed to free the pressure discs by means of a tension release pin 49 carried in an axial bore 50 in the stud and engaging the tank 46.

Movement of the lever 38 in a clockwise direction as viewed in FIG. 1 by operation of the bobbin thread re-. plenishing mechanism serves to release the needle thread tension device by virtue of a slide bar constrained for vertical reciprocation in the bracket arm by means of elongate slots 56 and shoulder fastening screws 57. The slide bar 55 bifurcated as at 58 to embrace a rounded free extremity 59 of the lever 38. The slide bar is formed with a laterally extending tang 66 which underlies one arm 61 of a bell crank tension releasing member fulcrumed at 62 in the bracket arm 13 and having another arm 63 disposed for engagement with the tension release pin 49 and also with a light return spring 64 for biasing the tension releasing bell crank 61, 63 out of tension releasing position.

Illustrated at of the drawings is a presser bar carrying a conventional presser foot at its lower extremity. Pivoted at 71 in the bracket arm is a presser bar lifting member 72 having a laterally extending pin 73 thereon disposed for engagement with the arm 61 of the thread tension releasing bell crank 61, 63 so that either the presser lifting lever 72 or the slide bar 55 may be responsible for operating the tension releasing bell crank 61, 63.

Referring to FIG. 4, the arm 61 of the tension release bell crank has a latch notch formed in one side which cooperates with a latch lug 81 formed on one arm 32 of a bell crank latch lever fulcrumed at 83 in the bracket arm and having another arm 84 extending upwardly Within a bracket arm. A light coil spring 85 engages the arm 84 of the bell crank latch lever for biasing the latch lever in a counterclockwise direction as viewed in FIGS. 2 and 3.

When the tension release bell crank 61, 63 is turned so as to release the tension device 453 as illustrated in solid lines in FIG. 2, the latch lug 81 of the latch lever 82, 34 will drop into the latch notch 3% thus constraining the tension release lever 61, 63 from returning even though the slide bar 55 should descend, until the bell crank latch lever e2, 84 is shifted by means of a cam member which is carried by the needle bar drive link 22 at its pivotal connection of the needle bar. The cam member t is positioned relatively to the bell crank latch arm 84 such that the latch will be engaged thereby and released when the take up member 21 occupies the highest point of travel as illustrated in dashed lines in FIG. 2. This position of the take up lever corresponds to the maximum expansion of a loop of thread engaged by the take up lever between the thread tensioning device 39 and the needle 24. The S2 of the latch lever 82, 84 is in addition to the latch lug 51 formed with a follower finger disposed in the path of travel of the pin 73 of the presser lifting lever 82 such that when the tension release lever 61, 63 is turned to release the tension device 49 by means of the presser bar lifting iernber 72, the latch lever 82, 84 will simultaneously be shifted by the pin '73 into an inoperative throwout position as illustrated in dotted lines in FIG. 2. When the presser device is lowered by the presser bar lifter lever 72 the tension release lever 61, 62 cannot therefore, be maintained effective by the latch lever 82, 3 and the needle thread tensioning device will be immediately restored to effectiveness.

Having thus set forth the nature of this invention what is claimed herein is:

1. In a sewing machine having a frame, stitch forming instrumentalities including a reciprocatory needle bar in said frame, drive means operatively connecting said stitch forming instrumentalitles for operation in timed relation, a needle thread tensioning device carried by said frame, a tension releasing member operatively connected to said thread tensioning device and shiftably supported on said frame, a plurality of separate means for effecting a shift of said thread tensioning member into and out of a position releasing said thread tensioning device, a latch member shiftably supported in said frame and engageable with said tension releasing member for constraining said tension releasing member in said position releasing said thread tensioning device, cam means associated with said stitch forming instrumentalities for releasing said latch member in only one predetermined position of said stitch forming instrumentalities, and a throw-out means for said latch member associated with one of said plurality of separate means for effecting a shift of said thread tensioning member.

2. In a lock stitch sewing machine having a reciprocatory thread carrying needle, a needle thread tensioning device, a bobbin accommodating loop taker, means for replenishing said bobbin in place in said loop taker with thread from said needle, a work presser device and a presser lifting device, a shiftable tension releasing member operatively connected to said needle thread tensioning device, a first tension release means operatively connected with said bobbin thread replenishing means for effecting a shift of said tension releasing member into a position releasing said needle thread tensioning device during replenishment of thread on said bobbin, a shiftable latch member engageable with said tension releasing member for constraining said tension releasing member in said position releasing said needle thread tensioning device, cam means associated with said needle for releasing said latch member only in a predetermined position of reciprocation of said needle, a second tension release means associated with said presser lifting device for effecting a shift of said tension releasing member into a position releasing said needle thread tensioning device while said work presser device is lifted, and a throw-out means for said latch member associated with said second tension release means.

3. A device as set forth in claim 2 in which said tension releasing and said latch members comprises bell crank levers and in which said presser lifting device comprises a presser lifting lever, and in which the axis of said tension releasing, latch, and resser lifting levers are parallel and spaced each from the other.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A SEWING MACHINE HAVING A FRAME, STITCH FORMING INSTRUMENTALITIES INCLUDING A RECIPROCATORY NEEDLE BAR IN SAID FRAME, DRIVE MEANS OPERATIVELY CONNECTING SAID STITCH FORMING INSTRUMENTALITIES FOR OPERATION IN TIMED RELATION, A NEEDLE THREAD TENSIONING DEVICE CARRIED BY SAID FRAME, A TENSION RELEASING MEMBER OPERATIVELY CONNECTED TO SAID THREAD TENSIONING DEVICE AND SHIFTABLY SUPPORTED ON SAID FRAME, A PLURALITY OF SEPARATE MEANS FOR EFFECTING A SHIFT OF SAID THREAD TENSIONING MEMBER INTO AND OUT OF A POSITION RELEASING SAID THREAD TENSIONING DEVICE, A LATCH MEMBER SHIFTABLY SUPPORTED IN SAID FRAME AND ENGAGEABLE WITH SAID TENSION RELEASING MEMBER FOR CONSTRAINING SAID TENSION RELEASING MEMBER IN SAID POSITION RELEASING SAID THREAD TENSIONING DEVICE, CAM MEANS ASSOCIATED WITH SAID STITCH FORMING INSTRUMENTALITIES FOR RELEASING SAID LATCH MEMBER IN ONLY ONE PREDETERMINED POSITION OF SAID STITCH FORMING INSTRUMENTALITIES, AND A THROW-OUT MEANS FOR SAID LATCH MEMBER ASSOCIATED WITH ONE OF SAID PLURALITY OF SEPARATE MEANS FOR EFFECTING A SHIFT OF SAID THREAD TENSIONING MEMBER. 